Dramatic reduction in Telemarketer calls

We have received ZERO telemarketer calls since Christmas. We are signed up on the Do Not Call Registry here in the US, and are registered with the Telephone Preference Service - as well as the other preference services from the Direct Marketing Association. Nontheless, we typically would receive at least a couple of solicitation calls each day. Well, my sister-in-law gave me a TeleZapper for Christmas, and I plugged it in as soon as I opened the package. We have noticed no solicitation calls since. I should mention here that we block anonymous calls, and we also use Caller ID to see who's calling before answering. If we don't see a name we know, we let it go to the answering machine. Well, now when the answering machine picks up (or when we pick up the receiver) a tone is played that makes predictive dialer machines think that our number is disconnected. We used to get a lot of "empty" messages on our machine - error tones when the solicitation caller hung up after our outgoing message. No more :-)